Why can't Xuan girls have healthy children?

Xuan Nv can't give birth to a healthy child, because she comes from skyclan, and the environment of the Yi people is not suitable for her to survive. Moreover, before leaving this country, she swore that as long as she betrayed Yin Si, her children would die and live alone. So many reasons put together, Xuan Nv could not have a healthy child after she got married and left the country.

Xuan Nv is the sister of Bai Qian's elder sister. Because she didn't want to marry a black bear, she fled to Qingqiu. Xuan Nv was jealous of Bai Qian's beauty, her affair and her departure, so she pretended to seduce her departure and alienated Bai Qian's feelings with her. When Bai Qian knew that she had left the country and betrayed herself, she was very sad and angry, but she wouldn't be with her. No matter what she says, Bai Qian will never forgive her for leaving the country. She lost Bai Qian, so he can only stay with Xuan Nv.

Xuan Nv got out of the country by trickery, but she didn't really love her when she left the country, so their married life was not happy, and Xuan Nv always couldn't give birth to healthy children, so Xuan Nv gradually got dark, and she felt that all this was caused by Bai Qian.